Metrological evaluation of the certification of primary reference materials characterized by high-precision constant-current coulometry for the reliability of the titration analyses

The use of pure materials in chemical analysis is currently in high demand due to the need to provide reliable measurement results. In the Electrochemistry Laboratory of the National Institute of Metrology from Brazil (Inmetro) is located the primary system of coulometry, which is considered the standard of the measurement for the amount of substance. The main function of this primary system is to certify primary reference materials to ensure reliability and metrological traceability for titration analyses. Some important certified reference materials (CRMs), homogeneous, stable, and characterized with an accurate property value have been developed. This work aims to present the stages for certifying the primary reference materials in a metrological approach: potassium hydrogen phthalate for acid-base titration, potassium chloride for precipitation titration, and potassium dichromate for redox titration. In addition, the key comparisons that were necessary to demonstrate the national traceability structure's equivalence for these CRMs' international recognition will be shown.